1. Field of the Invention
The present invention relates to a thin film piezoelectric element, a suspension assembly, and a hard disk drive.
2. Related Background Art
A thin film magnetic head for recording and reproducing magnetic information in and from a recording medium such as a hard disk is formed in a so-called head slider. This head slider is mounted on a tip region of a suspension assembly, thereby constructing a head gimbal assembly (HGA). In general, this suspension assembly is constructed by placing a flexible flexure over a load beam of stainless steel or the like, and read/write wires of the thin film magnetic head are provided on the flexure. The base end side of this suspension assembly is coupled to an actuator arm driven by a voice coil motor (VCM). A VCM coil or the like is attached to the interconnected structure of the suspension assembly and the actuator arm, thereby constructing a so-called head stack assembly (HSA).
With recent tendencies toward higher recording densities of hard disks, particularly, toward narrower track widths, there are demands for a technology of driving the head slider by a small amount with high accuracy. There was thus a conventional proposal of the head gimbal assembly in which a thin film piezoelectric element making use of a piezoelectric element was placed at the interconnected part between the suspension assembly and the actuator arm, as described in Japanese Patent Application Laid-Open No. 2002-134807. This is a so-called two step motion type assembly, in which the first step is to control relatively large movement of the thin film magnetic head by drive of the actuator arm by the voice coil motor and in which the second step is to control fine movement such as tracking compensation by drive of the suspension assembly by the thin film piezoelectric element.
In the head gimbal assembly of this two step motion type as described above, however, the whole of the long suspension assembly needs to be driven by the thin film piezoelectric element, and there was thus a limit to achievement of higher accuracy of tracking. For this reason, there is another proposal of an apparatus in which the thin film piezoelectric element is placed between the head slider and the suspension assembly, for example, as disclosed in Japanese Patent Application Laid-Open No. 2002-203384. In this apparatus, the thin film piezoelectric element does not have to drive the long suspension assembly itself, but is able to directly drive the head slider, thus achieving higher-accuracy tracking.
The thin film piezoelectric element disclosed in Japanese Patent Application Laid-Open No. 2002-203384 has a laminate including a piezoelectric film, and a pair of electrode films placed so as to sandwich the piezoelectric film in between. Furthermore, this thin film piezoelectric element has a resin film formed so as to cover the laminate, and an electrode formed on the resin film and electrically connected to the electrode film.